Fitness of Enfuvirtide-(T-20)-Resistant HIV-1

描述（由申请人提供）：人类免疫缺陷病毒1型（HIV-1）产生耐药性的突变也可能损害病毒的复制能力。多药耐药病毒复制能力的降低可能部分解释了在病毒学失败的情况下，含蛋白酶抑制剂方案的持续免疫益处。血浆病毒滴度仍然明显低于病毒设定点，这是由于失败方案的剩余活性和与野生型相比复制能力降低的综合影响。中断治疗消除了选择性压力，导致滤过性野生型病毒重新出现，这与病毒载量上升和CD4细胞计数下降有关。恩福韦肽（T-20）是一种新型的HIV- 1进入抑制剂，在体外和体内都具有很强的活性。这种由36个氨基酸组成的肽通过结合gp41外结构域的第一个七肽重复（HR-1）来阻断HIV-1的进入，从而阻止病毒与细胞融合所必需的发夹环的形成。HR-1中几个位置的突变赋予了对T-20的抗性。尽管对T-20的耐药性可以迅速发展，但临床研究数据表明，尽管出现了T-20耐药病毒，但T-20至少仍保持部分活性。初步数据表明，在没有药物的情况下，使用我们实验室开发的一种新型重组标记病毒试验，这些病毒在生长竞争试验中的适合度低于野生型。因此，我们提出了一系列的实验来进一步表征T-20抗性突变对HIV-1适应度、HIV-1进入动力学和毒力的影响。这些实验的具体目的是：1)比较T-20耐药病毒在有药和无药情况下的适应度；2)验证与T-20抗性相关的适应度损失与T-20持续抗病毒活性显著相关的假设；3)验证与T-20抗性突变相关的适应度差异是由于病毒-细胞融合率的差异造成的假设。这些研究的结果将提供对T-20耐药的分子、病毒学和临床后果的更深入的了解，并可能有助于指导T-20在挽救治疗中的应用。

DESCRIPTION (provided by applicant): Mutations in human immunodeficiency virus type 1 (HIV-1) that confer drug resistance may also impair replication capacity of the virus. Reduced replication capacity of multi-drug resistant viruses may explain, in part, the persistent immunologic benefits of protease inhibitor-containing regimens in the setting of virologic failure. Plasma virus titers remain significantly below the viral set point due to the combined effects of the residual activity of the failing regimen and the reduced replication capacity compared to wild-type. Removal of selective pressure by treatment interruption leads to re-emergence of the fitter wild-type virus that is associated with a rise in virus load and fall in CD4 cell count. Enfuvirtide (T-20) is a novel HIV- 1 entry inhibitor with potent activity in vitro and in vivo. This 36-amino acid peptide blocks HIV-1 entry by binding to the first heptad repeat (HR-1) of the gp41 ectodomain, thereby preventing formation of a hairpin loop that is essential for virus-cell fusion. Mutations at several positions in HR-1 confer resistance to T-20. Although resistance to T-20 can develop quickly, data from clinical studies suggest that T-20 remains at least partially active despite emergence of T-20-resistant virus. Preliminary data show that these viruses are less fit than wild-type in growth competition assays in the absence of drug using a novel recombinant marker virus assay developed in our laboratory. We therefore propose a series of experiments to characterize further the effects of T-20 resistance mutations on HIV-1 fitness, kinetics of HIV-1 entry, and virulence. Specific aims of these experiments are: 1) To compare fitness of T-20 -resistant viruses in presence and absence of drug; 2) To test the hypothesis that fitness loss associated with T-20 resistance is significantly correlated with persistent antiviral activity of T-20; and 3) To test the hypothesis that fitness differences associated with T-20 resistance mutations are due to differences in the rate of virus-cell fusion. Results of these studies will provide a deeper understanding of the molecular, virologic, and clinical consequences ofT-20 resistance, and may help guide the use of T-20 in salvage therapy.